1. Field of the Invention
The present invention relates to an inter-vehicle distance measuring system and apparatus for measuring a distance between a target vehicle (or the first vehicle) and the present vehicle (or the second vehicle) behind the target vehicle.
This application is based on Patent Application No. Hei 11-242346 filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
As a conventional inter-vehicle distance measuring apparatus, Japanese Unexamined Patent Application, First Publication, Hei 5-87914 discloses an apparatus using a radar. In the disclosed apparatus, an antenna is attached to the front face of the vehicle, so as to radiate an FM (radio) wave frontward, and generate a beat frequency signal by mixing a reflected wave from a target vehicle ahead of the present vehicle with the original waveform of the radiated FM wave, thereby detecting the position of the target vehicle based on the frequency of the beat frequency signal.
The present invention provides an inter-vehicle distance measuring system and apparatus employing a completely novel method, that is, completely different from the above conventional method employed in the conventional apparatus, and an objective of the present invention is to provide an inter-vehicle distance measuring apparatus which can measure the inter-vehicle distance regardless of weather conditions such as rainfall or snowfall, and which can be manufactured at a lower cost in comparison with the conventional apparatus using a radar.
Therefore, the present invention provides an inter-vehicle distance measuring system and apparatus for measuring a distance between a target vehicle ahead of a present vehicle (which is following the target vehicle) and the present vehicle, comprising:
in the target vehicle:
a first detecting section for detecting first road-surface data indicating a condition of a road surface on which the target vehicle is currently driving; and
a transmitting section for transmitting the first road-surface data to the present vehicle, and in the present vehicle:
a receiving section for receiving the first road-surface data transmitted from the target vehicle;
a second detecting section for detecting second road-surface data indicating a condition of a road surface on which the present vehicle is currently driving;
a time difference calculating section for comparing the first and second road-surface data, and calculating and outputting a time difference between each detection time of the first and second road-surface data when the first and second road-surface data have the maximum correlation; and
a computing section for calculating the inter-vehicle distance between the target vehicle and the present vehicle, based on the time difference output from the time difference calculating section.
In the above structure, the target vehicle transmits the first road-surface data, such as the roughness of the road surface, to the present vehicle. Also in the present vehicle, the second road-surface data such as the roughness is also detected, and both detected data are compared. In the present vehicle, the first and second road surface data having the maximum correlation are detected, and the time difference of each detection time of these data is calculated so as to calculate the inter-vehicle distance.
Accordingly, an inter-vehicle distance measuring system and apparatus employing a novel method (completely different from the inter-vehicle distance measuring system and apparatus using a radar) can be provided. In addition, the present apparatus is not affected by weather conditions such as rainfall or snowfall, and can be manufactured at a lower cost in comparison with the conventional apparatus using a radar.
The first and second detecting sections may be suspension stroke sensors for detecting strokes of changes of the suspension of each vehicle, or may be distance measuring sections for measuring a distance from the body of each vehicle to the road surface. In either case, the condition of the road surface below the vehicle can be accurately detected, thereby obtaining accurate road-surface data.
On the other hand, the first and second detecting sections may be sound detecting sections for detecting a sound generated by the suspension of each vehicle, or may be movement detecting sections for detecting contraction and extension of the suspension of each vehicle.
These detecting sections can be obtained at relatively low cost, thereby providing the apparatus at a lower cost.
Typically, the computing section calculates the inter-vehicle distance by multiplying the time difference output from the time difference calculating section by a driving speed of the present vehicle. In this case, the inter-vehicle distance can be calculated using a simple circuit arrangement.
When the compared first and second road-surface data have maximum overlap, the time difference calculating section may determine that both data have the maximum correlation.
On the other hand, when the compared first and second road-surface data have minimum non-overlap, the time difference calculating section may determine that both data have the maximum correlation.
In either case, the time difference for the road-surface data having the maximum correlation can be easily detected. Typically, the road-surface data is a waveform indicating the roughness of the road surface.
The present invention also provides an inter-vehicle distance measuring system and apparatus having two inter-vehicle distance measuring apparatuses as explained above, respectively provided for right and left wheels of each vehicle, wherein the inter-vehicle distance is determined based on results measured by the two inter-vehicle distance measuring apparatuses.
The present invention also provides an inter-vehicle distance measuring system and apparatus having an inter-vehicle distance measuring apparatus as explained above, and a radar inter-vehicle distance measuring apparatus provided in the present vehicle, wherein the inter-vehicle distance is determined based on results measured by the two inter-vehicle distance measuring apparatuses.
According to the above structure having a two-apparatus arrangement, the measurement accuracy can be improved, and the inter-vehicle distance measurement can be performed even if one of the apparatuses has a problem.